Lesson 1.1.3

1.1.3 page 2

Explore

In Lesson 1 you learned the divisions of the nervous system that sent information to the brain for processing.

In Lesson 2 you learned the specific parts of the brain that are responsible for processing information. You also learned that the brain communicates with structures in your body using motor neurons to produce a response. You will now learn about the structures and functions of the neuron, the basic cell of the nervous system.

 

Read

To help you understand neurons, read pages 368 and 369 of your textbook. Then read pages 370 to 372. You may wish to make summary notes and place your notes in you course folder for future study. It is important to include a labelled diagram of the neuron similar to the one on page 369 of your textbook.

 

dendrite: a branching  process of a neuron that receives input from other neurons or sensory receptors and transmits a nerve impulse toward the cell body
 
cell body: a part of a neuron that contains the nucleus and other cell organelles for carrying out the metabolic reactions of the nerve cell; relays the nerve impulse from the dendrites to the axon

axon: the process that emerges from the cell body and conducts the nerve impulse away from the cell body; the axon may be a metre long in motor neurons

Schwann cell: a type of supporting nerve cell that is found in the peripheral nervous system and wraps around axons of neurons and produces the myelin sheath

myelin sheath: a fatty insulating layer that surrounds axons that greatly increases the rate of impulse transmission

nodes of Ranvier: a tiny gap in the myelin sheath surrounding the axon of myelinated neurons; nerve impulse transmission occurs between nodes of Ranvier in what is called salutatory conduction which causes the increase in the speed of impulse transmission

axon terminal: numerous endings found at the end of an axon; axon terminals are enlarged into knobs that are specialized for producing neurotransmitters

You are now familiar with the receiving area called the dendrite, a cell body that carries out the life functions of the nerve cell, and the sending structure called the axon. Motor neurons communicate nerve impulses rapidly to effectors. They are myelinated, which means their axons are surrounded by Schwann cells. Schwann cells produce a fatty material called myelin sheath, which insulates the axon. In Lesson 7, you will learn how the nodes of Ranvier help to increase the speed of nerve impulse transmission. The axon terminals have many bulbous knobs that produce neurotransmitters. In Lesson 8, you will learn how neurotransmitters complete communication between neurons. These neurotransmitters are necessary because neurons are not physically joined together.

Inquiry into Biology (Whitby, ON: McGraw-Hill Ryerson, 2007), 372, fig. 11.9. Reproduced by permission.

 

Watch and Listen

To review the structures of the neuron, you may want to watch the video below.
Neuron Anatomy

Self-Check

You should now be able to describe the three types of neurons and describe the structures and functions of the parts of a neuron.

 

SC 1. Match the following functions to their respective structures indicated on the image below. Identify and write the name of the correct structure in the space provided corresponding to that structure’s number on the diagram.

Functions:

  • performs life functions and relays messages to the axon
  • the control centre of the cell
  • receives input from other neurons of sensory receptors and transmits toward the cell body
  • a fatty insulating layer that increases the rate of communication transmission
  • gaps in the myelin sheath that increase the rate of communication transmission
  • transmits nerve impulses away from the cell body
  • a type of supporting nerve cell that wraps around axons in the peripheral nervous system and produces myelin

 

This is a diagram that students label and then autocheck themselves.

Inquiry into Biology (Whitby, ON: McGraw-Hill Ryerson, 2007), 372, fig. 11.9. Reproduced by permission.

 

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